Heretofore, methods have been proposed for treating subsurface earth formations for the purpose of reducing the rate of movement of the fluid materials through selected parts of the formation. Included in the prior art technologies are the in-place formation of gels, either by surface prepared materials that are pumped into the well to become operative at a particular time after their first introduction into the well or by the introduction of several components at different times with an introduction procedure that combines one or more of the materials in the formation where the selective permeability reduction may be desired. Most of these prior art systems have been somewhat ineffective because of the inability to control the actual placement of the materials into the position in the formation where the formation treatment is desired.